My personal preference is Ubuntu. My web site http://www.sailfun.co.uk
runs on a Dell desktop with Ubuntu server edition running on it.
However, you are talking about Laptops and end users. I built an old Toshiba Laptop with Ubuntu on it. There are quite a lot of 'issues' switching to Linux from XP or Vista, it doesn't all work the same way. You get a LOT more performance out of the hardware using Linux, but you loose a lot in 'learning curve'.
So much so, when I recently bought my wife a 'NetBook' I opted for a Samsung NC10 with XP on it, she isn't that familiar with computers and a change would have caused a lot of issues.
One advantage of Linux, is there are lots of free - opensource - products, such as GIMP for graphical editing, once you find out about these you will also find that many also have Windows versions too!
If you have an old computer that struggles with Windows (XP), try rebuilding it with Ubuntu (you only need to burn a CD and follow the instructions), you can even make a dual-bootable system simply, so you can switch between the two.
Try it and see. But dont try it on your bestest PC - just incase you muck it all up!